Air conditioning system employing a hygroscopic medium



Mafch 16, 1954 w. L. MCGRATH AIR CONDITIONING SYSTEM EMPLOYING A HYGROSCOPIC MEDIUM Filed Jan. 12, 1951 FIG.3

FIG.4

- INVENTOR. 11/4164, 1 r a! Patented Mar. 16, 1954 AIR CONDITIONING SYSTEM EMPLOYING A HYGROSCOPIC MEDIUM William L. McGrath, Syracuse, N. Y., assignor to Carrier Corporation, Syracuse, N. Y., a corporation of Delaware Application January 12, 1951, Serial No. 205,630

6 Claims.

This invention relates to air conditioning units and more particularly to the introduction of a hygroscopic medium in an air conditioning unit to achieve greater capacity, to effect a substantial reduction in initial cost of the unit, and to provide lower relative humidity.

The chief object of the present invention is to provide an economical air conditioning unit for conditioning air to provide a lower relative humidity which permits substantial reductions in operating costs.

A further object is to provide an air conditioning unit for conditioning air to provide a lower relative humidity in which the size of the compressor employed in the unit is reduced in comparison with units heretofore known to achieve a great reduction in initial and operating costs.

A further object is to provide an air conditioning unit in which hygroscopic medium'is employed to provide greater flexibility as to arrangement of components of the unit, and to effect a great reduction in initial and operating costs of the uni. Other objects of the invention will be readily perceived from the following description.

This invention relates to an air conditioning system which comprises in combination a first air passage containing the evaporator of a refrigerating system, a second air passage containing the condenser of the refrigerating system and fans to direct streams of air to be cooled or heated respectively through the air passages. Means are provided in the first passage to distribute a hygroscopic medium over the evaporator in the path of the first air stream to remove moisture therefrom. At least a portion of the hygroscopic medium carrying removed moisture is transferred to the second passage and distributed over the condenser in heat exchange relation with the second air stream, thus removing moisture from the hygroscopic medium to concentrate the same. The concentrated hygroscopic medium is then returned to the first passage and is again distributed'over the evaporator in the path of the first air stream to remove moisture therefrom.

The attached drawings illustrate a preferred embodiment of my invention in which:

Figure l is a diagrammatic view of an air conditioning unit embodying the present invention;

Figure 2 is a skeleton psychrometric chart illustrating the principle of operation of the invention;

' Figure 3 is a fragmentary view illustrating a 2 modification of the mechanism for distributing hygroscopic material in the path of the air streams passing through the unit; and

Figure 4 is a diagrammatic view illlustrating a modification of the invention.

Referring to the drawings, there is disclosed in Figure 1 an air conditioning unit including a casing 2 separated by a partition 3 into two air passages 4 and 5. The usual louvre openings 6 are provided in each passage 4 and 5 to permit air to be directed through casing 2. Afan I is provided in passage 4 to draw air therethrough and to discharge such air into the area being conditioned. A fan 8 is provided in air passage 5 to draw air therein and to discharge the air from the casing 2.

A refrigeration system is provided to cool the air drawn through passage 4. The refrigeration system includes the compressor 9 preferably disposed in passage 5, and connected to condenser l0 placed in passage 5 by discharge line H. Condenser I0 is connected to evaporator l2 placed in passage 4 by liquid line 13. A capillary tube l4 for example is placed in line 13 to regulate the quantity of refrigerant passing to evaporator l2. Evaporator I2 is connected to compressor 9 by suction line l5.

A sump 16 preferably is formed in the lower portion of casing 2. Sump l6 preferably is divided into two portions, 11 and I8, portion I! being placed in passage 4 While portion [8 is placed in passage 5. A weir I9 is placed in sump It to regulate the flow of medium'from portion is to portion l1. Hygroscopic material such as tri-ethylene glycol is contained in sump Hi. It will be understood, of course, other hygroscopic materials may be employed in the present invention; for example, water solutions or brines of the chlorides or bromides of various inorganic elements such as lithium chloride, lithium bromide and calcium chloride may be employed. A pump [9 circulates medium from portion I! through line 2!} to nozzles 2| which sprays the medium over the surface of evaporator l2, the medium flowing down such surface and returning to portion I! of sump l6. Preferably, a bypass line 22 is connected to line 20 to direct some portion of medium to passage 5, such medium being sprayed through nozzle 23 over the surfaces of condenser It] or if desired, permitting the medium to flow into the sump portion IS. A valve 24 may be placed in line 22 to permit the amount of medium directed to passage 5 to be regulated.

A pump 25 withdraws medium from sump portion 18 and distributes such medium over the surface of condenser It through line 2% and nozzles 27, the medium after passage over the surfaces of condenser is returning to sump portion it. As the level in sump portion it rises, some portion of concentrated medium therein overflows the weir 9 to raise the level of medium in sump portion H. Preferably, the concentrated medium and diluted medium are placed in heat ex change relation by directing the diluted medium through a coil (not shown) placed in the sump or by directing line 22 through sump i8. Liquid line It may pass through sump portion iii in heat exchange relation with medium in such portion of the sump.

Considering the operation of the device, fan i directs air to be treated through evaporator I2. Pump it withdraws hygroscopic medium from sump portion I! and sprays the medium through nozzles 2| on the surfaces of evaporator [2, in heat exchange relation with air passing there through. Spraying the medium over the evaporator surface increases the cooling capacity of the evaporator because a lower equilibrium vapor pressure is established by the medium, thereby removing more moisture from the air than would occur without the use of the medium. A small quantity of the medium is directed through by-pass 22 to passage for reconcentration.

Pump 2:: sprays medium for pump portion iii over the surfaces of condenser l0, thereby raising the equilibrium vapor pressure of the medium above the prevailing outside air dew point causing the water to be evaporated into the air stream for discharge outside of the enclosure in which the unit is placed, the concentrated medium returning to the sump portion Hi. The concentrated medium continuously flows over weir id to sump portion I1 in an amount corresponding to that bled off through by-pass 22. through passage 4 is cooled and dehumidified while the heat so transferred to the refrigerant and to the hygroscopic medium is removed in passage 5 since the stream of air directed through condenser It condenses refrigerant therein and r removes moisture from the hygroscopic medium sprayed on the surfaces of the condenser.

The .unit as described above possesses considerably more capacity then a conventional refrigeration cycle including the same compressor, condenser, and evaporator. The air distributed from the unit through passage 4 is at a reduced temperature and at a very low dew point. Under some circumstances, it may not be desirable to utilize such a large amount of clehumidifying capacity. In such circumstances, the dehumidifying capacity can be converted to sensible cooling capacity by the addition of moisture tothe air stream leaving passage d. If desired, an atomizing spray nozzle 23 is placed in the path of air leaving the evaporator, nozzle 28 being connected by line 29 to a suitable source of supply.

For purposes of control of the addition of water to the leaving air stream the solenoid valve 38 may be placed in line 29, solenoid valve t8 being controlled by means of a thermostat 3i. Thermostat 3| may be a common two step type control responsive to a drop in temperature of the room in which the unit is placed. Upon a predetermined drop in room temperature, the solenoid valve is closed to reduce the sensible cooling capacity of the unit while increasing the dehumidifying effect which is a desirable operating condition under reduced loads and prevents a Air directed rise of room relative humidity on partial load operation. A further drop in room temperature may actuate the thermostat 3| to discontinue operation of compressor 9. While I have disclosed a two step on and off type of control, it will be understood that in larger systems a modulating type of control may be employed.

In Figure 2,, I have illustrated on a skeleton psychrometric chart the principle of operation of the air conditioning unit described above. Referring to Figure 2, assuming a conventional refrigeration system operating with an evaporator surface temperature B upon air to be treated at condition A, air may leave the unit at condition C. The total heat removal would correspond to the enthalpy difference hi. When a hygroscopic medium is sprayed over the evaporator with the same air quantity and the same surface temperature, the equilibrium condition will be at a lower lever D. For example, assuming 77% tri-ethylene glycol employed as the hygroscopic medium, this equilibrium condition will be at a dew point 18 lower than the surface temperautre B and at the same dry bulb temperature. The air will then leave the unit at condition E. The total amount of cooling is represented by the enthalpy difference b2.

If it is desired to have greater sensible cooling capacity in place of dehumidifying capacity, moisture is evaporated in the air stream to cause adiabatic cooling from, for example, condition E to condition F. This represents substantially the same sensible heat factor in the room as a conventional system but results in a greatly increased cooling capacity as represented by the line AF as compared to the line AC.

It will be appreciated that with a given compressor it is impossible to maintain the same surface temperature after the medium is sprayed on the evaporator. However, when medium is sprayed over the evaporator the compressor capacity and the evaporator capacity balance off at a dew point at a higher refrigerant temperature with an increase in capacity of the evaporator. The usual objection to designing to a high refrigerant temperautre is not present because the dehumidifying capacity obtained from the medium more than offsets the loss of dehumidification resulting from the increase in refrigerant tempertaure.

While I have described sump It as extending beneath the condenser and the evaporator of the refrigeration system, it will be appreciated separate sumps may be provided together with means to return concentrated solution to passage 4 and to supply diluted medium to passage 5 for concentration.

In Figure 3, I have illustrated a modification of my invention in which pumps l9 and 25 are eliminated. In this case slingers 33 may be employed to distribute medium over the surfaces of evaporator I2 and condenser iii. A gutter 34 may be provided to pass a desired portion of diluted medium to passage 5. Heat exchangers, as described above, may be provided if desired.

In Figure 4, there is illustrated a modified selfcontained air conditioning unit which comprises a casing 45! separated by a partition 4! into air passages 52 and 43. A sump 44 is provided adjacent the bottom of casing 46. Sump 44 may be similar to sump it as described above. A filter or air washing member 45 is placed in passage 22, air being drawn through such passage and discharged into the area being treated by fan 46. A second air washing member 4'! is placed in pasplaced in sump portion 50 in heat exchange relation with hygroscopic medium therein. The condenserv may also be a double pipe interchangerand is placed in sump portion 52 in heat exchange relationwith hygroscopic mediumtherein. A pump 53 withdraws medium from sump portion 553 and sprays the same over filter in heat exchange relation with air passing through passage 42. Pump 53 also forwards some portion of .such medium to passage 43 for reconcentration as shown at 53'. A second pump 54 sprays medium to be concentrated over memb'erj'4i. The concentrated medium returns to sump portion by any suitable'means. The medium is cooled by evaporator 49 and is sprayed over'the surfaces of filter 45 by pump 53. Air to be treated is directed through filter 45 in heat exchange relation with the cooled medium sprayed thereon, thus cooling and removing moisture from the air being treated. The medium is reconcentrated in passage 43 because it isheated by condenser 51 and an equilibrium dew point obtained which is higher than the outside air dew point, thus the outside air passing through member 41 carries off the moisture removed at member 45 reconcentrating the medium.

The modified unit illustrated in Figure 4 as well as the unit shown in Figure 1 provides a substantial reduction in cost because of less heat transfer surface and provides effectively greater capacity for the same suction pressure because the solution gives an equilibrium dew point perhaps 10 lower than would be obtained on straight air cooling. Another advantage of such unit resides in the fact that the filter is selfcleaning since it is used for wetted surface as well as air cleaning. Greater flexibility as to arrangement of components in the casing is permitted since no problem exists as to levels or water disposal.

The present invention provides an air conditioning unit of improved design and more economical manufacture. The present unit permits smaller heat exchange surfaces and a smaller size of compressor to be employed than is customary in air conditioning units of conventional design. The present invention permits smaller units of similar capacity to be provided and permits similar size units of greater capacity to be employed. The present invention provides a substantial reduction in cost and permits increased flexibility with regard to arrangement of components of this system.

While I have described a preferred embodiment of my invention, it will be understood my invention is not so limited since it may be otherwise embodied within the scope of the following claims.

I claim:

1. In an air conditioning unit, the combination of a first air passage, a second air passage, a refrigeration system including a first heat exchange member in the first passage and a second heat exchange member in the second passage, means for directing a stream of air through the first passage, means for directing a second stream of air through the second passage, means to place a hygroscopic medium in heat exchange relation with the first member and in heat exchange relation with the first air stream to remove mois- 6 ture therefromymeans for supplying at least a" portion of the diluted hygroscopic medium to the second passage, means in the second passage to place the diluted hygroscopic medium in heat exchange relation with the second member and in heat exchange relation with. the second air stream to transfer moisture thereto thereby concentrating the medium, andmeans for returning concentrated medium to the first passage, and means to evaporate moisture in the air stream leaving the first heat exchange member. s

2. An air conditioning unit according to claim 1 in which a thermostat is provided responsiveto a change in area temperature to actuate the evaporating means.

3. In an air conditioning unit, the combinationof a first air passage, a second air passage,

a sump containing hygroscopic medium, hygroscopic medium in one portion of the sump beingconcentrated to a greater degree than hygro-'- scopic medium in a second portion of the sump, a filtering member in the first air passage, a distributing member in the second air passage,

means for directing an air stream through the first passage, means for directing a second air stream through the second passage, a refrigeration system including a first heat exchange member in the first sump portion and a second heat exchange member in the second sump portion in heat exchange relation with medium therein, means for distributing cooled hygroscopic medium over the filtering member in th path of the first air stream to cool the air and to remove moisture therefrom, means for supplying diluted medium to the second passage in heat exchange relation with the second heat exchange member to heat the medium, means for distributing heated diluted medium over said distributing member in the path of the second air stream to concentrate the medium, and means for supplying concentrated medium from the second portion of the sump to the first passage.

4. A method of air conditioning in which the steps consist in cooling a stream of air to be conditioned while simultaneously placing a hygroscopic medium in the path of the stream to remove moisture therefrom, bleeding a portion of the hygroscopic medium into the path of a second air stream, concentrating the medium by passing it through a heat exchanger placed in the path of the second air stream, and returning the concentrated medium to the path of the first air stream, and spraying moisture in the first air stream after its passage in heat exchange relation with the hygroscopic medium to reduce the dry bulb temperature of the first air stream.

5. In an air conditioning unit, the combination of a casing, a partition in the casing cooperating therewith to form a first passage and a second passage, means to direct a stream of air through the first passage, means to direct a stream of air through the second passage, a refrigeration system in the casing including an evaporator in the first passage in the path of air directed therethrough and a condenser in the second passage in the path of air directed therethrough, means to distribute a hygroscopic medium over the evaportor in the path of air to be conditioned to remove moisture therefrom, means for supplying at least a portion of the diluted. medium to the second passage, said concentrated medium and diluted medium being placed in heat exchange relation, means to distribute the diluted medium over the condenser in the path of the second air stream to remove moisture there- 7 from, a sump" in" the bottom of said casing, and means in said sump to regulate flow of concentrated medium from the second passage to the first passage.

6. In an air conditioning system, the combinationv of a first air passage, means to direct air to be conditioned through the passage, a second air passage, means to direct air through the second passage, a refrigerating system including an evaporator placed inthe path of the air directed through the first passage, and a condenser for condensing. refrigerant placed in the second passage, means to supply hygroscopic mediumto the 8 second passage, means for distributing some portion of said hygroscopic medium over the condenser in the path of the second air stream to transfer moisture to the second air stream thereby concentrating the medium, and means for returnin concentrated hygroscopic medium to the first passage, said hygroscopic medium supplied tothe second passage being placed in heat ex change relation with hygroscopic medium retur'm ing? to the first passage.

WILLIAM L. MG'GRATH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date I 2,091,159 Persons Aug. 24, I937 2',243',i7 8 Knoy May 2'7, 1941; 2,269,053 Crawford ...i Jan. 6, 1942 2,321,137 Gerard --s June 8-, 1943 

